Cataplexy

Cataplexy is a sudden and transient episode of muscle weakness accompanied by full conscious awareness, typically triggered by emotions such as laughing, crying, or terror. Cataplexy affects approximately 20% of people who have narcolepsy, and is caused by an autoimmune destruction of hypothalamic neurons that produce the neuropeptide hypocretin (also called orexin), which regulates arousal and has a role in stabilization of the transition between wake and sleep states. Cataplexy without narcolepsy is rare and the cause is unknown. The term cataplexy originates from the Greek κατά (kata, meaning "down"), and πλῆξις (plēxis, meaning "strike") and it was first used around 1880 in German physiology literature to describe the phenomenon of tonic immobility also known as "playing possum" (in reference to the opossum's behavior of feigning death when threatened). In the same year the French neuropsychiatrist Jean-Baptiste Gélineau coined the term 'narcolepsy' and published some clinical reports that contain details about two patients who have similar condition as the narcoleptic cases nowadays. Nevertheless, the onset reported by him was in adulthood as compared to the nowadays cases reported in childhood and adolescence. Even if he preferred the term 'astasia' instead of 'cataplexy' the case described by him remained iconic for the full narcoleptic syndrome. Cataplexy manifests itself as muscular weakness which may range from a barely perceptible slackening of the facial muscles to complete muscle paralysis with postural collapse. Attacks are brief, most lasting from a few seconds to a couple of minutes, and typically involve dropping of the jaw, neck weakness, and/or buckling of the knees. Even in a full-blown collapse, people are usually able to avoid injury because they learn to notice the feeling of the cataplectic attack approaching and the fall is usually slow and progressive. Speech may be slurred and vision may be impaired (double vision, inability to focus), but hearing and awareness remain normal.